Okay good, because I have a bunch of those kind. I kept seeing others mention large stamps as if they are required whether it's international or not and I didn't want to buy more just to find out these were just fine. Thanks!

The stamps you have are fine.

You need to focus on International rules only. Those sizes and general info can be found here:

http://www.royalmail.com/personal/international-delivery/international-standard

All you need to do is get the corresponding [u]International[/u] price for your item and use enough stamps to cover it {up} You can use any stamps including the ones you have.

[u] It is that simple I promise.[/u]

Write out your SASE
Use the Royal Mail calculator to get your price. http://www.royalmail.com/price-finder
Use a normal calculator to see how many 1st class stamps needed to meet/exceed that price- each stamp you have is worth £0.63.
Stick that number of stamps on your SASE.

DONE!

:mrgreen:

Hi, quick question as I've now been seeing this and am now confused. What size UK stamp should go on a 9"x12" SASE that is returning from the [uk] UK to the [us] US? I know 1st/2nd class is speed, and doesn't apply to international, but is it the same with size? Like, I have small 1st class stamps, which are valid for items up to 240mm x 165mm - does that matter or should I buy large stamps? Thanks

These are the 1st class stamps I have:
http://shop.royalmail.com/stamp-books/6-x-1st-class-stamp-book-change-of-phone-number/invt/20140786